Improvement in trusses for bridges



ofA two combined trusses.

vvare key-braces.

support the upper chords.

UNITED STATES PATENT OFFICE.

JOHN I. AVERY, OF NORlVICl'I, CONNECTICUT.

IMPROVEMENT IN TRUSSES FOR BRIDGES.

Speciiication forming part of Letters Patent No. 33,629, dated November 5, 1861.

' thereof, reference being had to the accompanying drawings, and to the letters of reference marked thereon, in which- Figure I is a perspective view. Fig. 2 is a perpendicular elevation; Fig. 3, a cross-section, and Fig. 4 a perspective view showing rail or carriage way.

In the drawings, A A are the upper chords Each chord is held in its place by two sets of braces and by iron vbeing the base-chord uniting the two trusses.

C OG C are main braces, and D D D D Both main. and key braces E E are chucks for the purpose of securing firmly the ends of the main and key braces in their proper places at the point of contact with the upper and lower chords.

f F F are iron rods passing through the lower chords B B B, and are secured at each end by the nuts fjl, which are screwed uponthe ends of the rods, and are prevented from sinking into .the timberl by means of large iron plates or wash ers.

G' G are iron rods. connecting the upper chord in each truss with the lower chords of lthe same truss, and these rods are secured at l each'end by the nuts g g, which are screwed upon the end sl of the rods, and also rest upon large iron plates or Washers to prevent their sinking into the timber.

The nature of myinvention consists in the combination of two sets of braces standing on two base-chords and terminating at the top in one chord, so as to resemble in a crosssection the letter V inverted, thus A, which .combination forms one truss. I then combine two or more trusses by making one set of braces in each truss nn-ite or stand on the same base-chord' resembling the letter W inverted, thus M, which combination of braces forming a series of angles forthe support of the upper chords etlectually prevents the lateral swaying to which bridges of a long span, or that are located where there is a curvaturc in the road, vare almost invariably subject, for the two upper chords are braced in such a way that it is impossible `for any amount of force to give them-eitheran outward orinward inclination, while at the same time the bridge has all the strength that the materials composing it can give.

To enable others skilled in the art to make and use my invention, I will proceed to describe its construction and operation.

I construct my trusses of timber such as/ is ordinarily employed in building bridges, using iron rods, nuts, and washers in the manner shown in the drawings'. The base-chords in the trusses rest upon the abutnients at each end of the bridge.

When my trusses are to be used in railroadbridges, I combine two trusses having three base and two upper chords, and place the ties for the rails upon the upper: chords, making what is called a deck bridge. Bridges for highways across large rivers may be constructed in the same manner; but it will often be found convenient to construct a bridge with the two trusses separate instead ot' being combined, and in such cases I use four base-chords and two upper chords and the trusses form the sides of the bridge, the rail orcarriage way rest ing upon sleepers supported by the upper and lower chords together. The timbers for the chords should be square and are placed in the truss edgewise, or so that a line drawn through the opposite angles will be horizontal. The chucks are set in mortises in the chords. The main braces,beginning at each end of the bridge or truss, are set with an inclination toward the center of lthe bridge, where they meet and form an angle with each other at the point of contact with the upper chord'.

.The key-braces may be set at an angle correon the chucks by screwing up the iron rods.

',iho bridge is crowned by connnenoing` :it the l formed by making one Set of braces in cach ends and screwing up each of the rods that. truss unite or stand ou the same base-chord pass through the upper chords. l .the whole being constructed substantially as That I Claim as my invention, and desire herein described, and for Jthe purposes Set to secure by Letters Patent, isforth.

The Combination of two sets of braces stsnd- .TOT IN' P, AVERY. in.,1 upon two base-chords :md terminating at Witnesses:

the top in one chord, forming a truss, and also the combination of two or more trusses thus GEO. PRATT, IIIRAM B. CROSBY. 

